Process for preparing calcium sorbate



United States Patent C 3,365,488

Patented Jan. 23, 1968 3 365 488 invention consist in that the preparation of calcium sorbate may practically be carried out in one process stage PR C S REPARlN C IU RBATE g g gg f fi g g x ig and only and that troublesome and expenslve process steps Hans Joachj;n schmidt,Frankfurt am Main Germany, for example filtration or centrlfugmg and washing are assignors to Farbwerke Hoechst Aktiengesellschaft 5 avolded' vormals Meister Lucius & Bruning, Frankfurt am Main, The followmg examples serve to illustrate the mven- Germany, a corporation of Germany tion but they are not intended to limit it thereto. No Drawing. Filed Dec. 8, 1964, Ser. No. 416,890 EXAMPLE 1 Claims priority, application Germany, Dec. 12, 1963,

F 41,520 224 grams of finely ground sorbic acid having a bulk 8 Clalms' (CL density of 0.42 gram/cc. and 56 grams of pulverized cal- The present invention provides a process for preparing cium OXlde were heated 60 to under a Pres calcium sorbate sure of 400 mm./Hg Wh1le stirring. A strongly exother- It is known to prepare calcium sorbate which is an mic reaction set in. After the reaction temperature had portant preservative for f d t ff by double decorm fallen, the mixture was further stirred for 30 minutes at position by mixing the solutions of a soluble salt of sorbic under a Pressure of film/Hg 1n Order acid, for example Sodium sorbate or potassium sorbate the water. There were obtained 260 grams of calclum sorand of a soluble salt of calcium, for example calcium bate of at least 99% f f having a bulk denslty of chloride or calcium acetate, in Water or in alcohol, the gram/ca The gram Sue was below sparingly solllilble calcium sorbate being1 precipitated. 20 EXAMPLE 2 A process as also been described w ich comprises reacting sorbic acid with calcium hydroxide in an aqueous 224 i Pglvenzed g ss suspension with the addition of sorbic acid in excess and grams 0 ca clllm m were mlxe un er n ge of a Wetting agent in order to bring about a complete cona flask provided with a stlirer unqer pressure of 200 version of calcium hydroxide. Both processes have the E H After i f f i ggi gE g; disadvantage that the calcium sorbate prepared by them t ntlxture If? er f e d O 1 o b t at must be filtered or centrifuged and freed from impurities 3 mmutes ere was 0 i a 5 i sor a e Such as foreign Salts or Wetting agents, by Washing cab least 99% strength. The median grain me of the calcium cium sorbate is obtained, however, in a very fine crystaliz l line from and it adsorbs impurities and solvents very per- 1 f l Orb t b manently so that process steps such as filtration or cenn g 9 p 3 ca E S S e trifuging and washing are very tedious and expensive. In it 0 10 i fi s y f g; addition the calcium sor-bate prepared according to the e i i d i i f i i the are last-mentioned process contains unreacted sorbic acid in Pnses m 6 y a mlxmg mac S y varying amounts. in the form of finely pulverized solids having median The present invention is based on the observation that i of less i i %2 1 1 h th r in pure calcium sorbate can be prepared by intimately mixg 2 alme m c alm W erem e g a ing finely pulverized sorbic acid with stoichiometrical ess an d 1 1 h th reacfon amounts of finely pulverized calcium hydroxide and/or .process as c alme In c W erem e 1 Calcium oXide 40 1s carrliled out at a subatmospheric pressure of 200 to 400 According to the present invention the salt is formed in the absence of solvents, diluents or wetting agents. process as dimmed m 0.1mm 1 Wherem the reactlon The finely pulverized or ground initial Substances '18 mitiated by heating the mixture to a temperature of (H h h from about 40 C. to about 80 C. zih ly les s th iui j0 2, d di r e sgh rfd iig zia irtiiiniggbgig 5. A process as claimed in claim 1 wherein the reaction bulk density of sorbic acid of less than 0.5 gram/cc. and 1S OmPleted 3 heatmg the mjxmre a temperature of of calcium hydroxide or calcium oxide of less than 0.4 from about 40 to about gram/cc 6. The process as defined 1n claim 1 where1n the re- The solid initial substances are intimately mixed in actant wlth sorblc acldls calclllm hyilhoxlda b t b known manner mechanically, for example, in reaction In a proqess p pr.eparmg.ca Cling vessels provided with stirrers or vibratory mixers, in vacaction of sofblc ac1d with 9 hy roxldetcflllcmm uum paddle dryers or in fluidization reactors. i q i mlxtme f i the lmprovemmt com- When carrying out the process of the present invention prises intimately admixmg the reactants, at a su. atmosit is advantageous to remove the water formed during the p her 10 pressure of 200 to 400 while they are m reaction by applying a Suitable subatmospheric pressure the form of finely pulverized SOlldS having median gram 1 sizes of less than 70 and heating said mixture to atemg i fi i zg i z gfi a 2 1 52 zgz fi g g i g perature of from about 40 C. to about 80 C. to lnitiate is also advantageous to initiate the reaction by heating and complete the reaction 8. The process as defined in claim 7 wherein the reto 40 C. to 80 C. When calcium hydroxide is used it IS actant with sorbic acid is Calcium oxide.

not necessary in most cases to heat the mixture, since the reaction between the finely ground sorbic acid and the References Cited finely ground calcium hydroxlde normally starts spontaneously when the reactants are thoroughly mixed. In UNITED STATES PATENTS order to achieve a complete conversion it is, however, ad- 2,833,745 5/ 1958 Fikentscher 260-526 vantageous to heat the reaction mixture to about 80 C. 3,021,354 2/1952 Cornell 6t 31 60-5 6 after the exothermic reaction has ended. This process step 3,139,378 6/1964 GOOdiIlg 260526 jjg j gfigjfi f drymg by applymg a Pressure LORRAINE A. WEINBERGER, Primary Examiner.

The advantages of the process according to the present I. R. PELLMAN, V. GARNER, Assistant Examiners. 

1. IN A PROCESS FOR PREPARING CALCIUM SORBATE BY REACTION OF SORBIC ACID WITH CALCIUM HYDROXIDE, CALCIUM OXIDE OR A MIXTURE THEREOF, THE IMPROVEMENT WHICH COMPRISES INTIMATELY ADMIXING THE REACTANTS WHILE THEY ARE IN THE FORM OF FINELY PULVERIZED SOLIDS HAVING MEDIAN GRAIN SIZES OF LESS THAN 70U. 